Dodge's heaviest commercial truck combines a beefy chassis with a cab from the 1500 series pickup.

Hmm. Looks like a big pickup, doesn't it? Well, yes and no. This new Ram 5500 HD does have the same cab as Dodge's popular 1500, 2500 and 3500 pickups, but it sits on a beefy chassis with straight rails behind the cab and suspension components designed to handle its rated weight of 19,500 pounds gross. It's been more than 30 years since Dodge built a truck this heavy, and together with the slightly lighter 4500 HD, rated at 16,000 pounds, the new Chrysler LLC is seriously going after the midrange market.

Dodge Truck marketers say their medium-duty sales assault actually began in the fall of 2006 with the Ram 3500 HD Cab Chassis, which went from virtually zero in the Class 3 conventional-cab category to almost one-third of the market in about a year. This is proof that buyers were impressed enough with the product and its pricing to try them. Its principal competitors - Ford and General Motors - have noticed. With Dodge's new 4500/5500 HD, the competition, and customers, have something else to consider.

The Ram 5500 HD's chassis design comes from the 3500 HD, and is beefed up to handle extra weight. This includes frame rails 7.7 millimeters (1/3 inch) thick (versus 5.7 mm on the 3500) along with stronger suspensions, axles and brakes. Rear frame rails are the industry standard 34 inches apart, and are straight and clean on top for easy body mounting. Like other builders, Dodge has worked hard to accommodate many types of bodies so the vehicle is more desirable to upfitters and buyers.

This truck had 4-wheel drive, with a Magna front-driving axle and a Dana S-111 rear, and a wheelbase of 188.5 inches. Like all Ram 4x4s, it sits rather high. The cab floor was 27.5 inches above the pavement, which made entry a side-step and pull-yourself-in exercise, at least for short guys like me. But a big grab handle on the A-pillar helped a lot. Four-wheel drive is engaged by a floor lever that's linked directly to the transfer case (an electric rotary switch actuator is an option). Shifting between 2-Hi and 4-Hi was easy, and so was going into and out of 4-Lo, after stopping and putting the tranny in Neutral. There was some thumping from the front end while going over bumps and the steering tends to wander from a straight line, but this is not unusual in Dodge 4x4s.

The only engine available in the 4500/5500 is the strong Cummins Turbo Diesel, also from the 3500 HD, with 6.7 liters (409 cubic inches) in displacement and rated at up to 305 horsepower and 610 pounds-feet of torque. The engine is EPA '07-legal and has a particulate filter and other advances, so it emits no smoke and absolutely no odor. It started almost instantly whether warm or from a 17-degree cold soak the morning after a 6-inch snowfall in central Ohio. Before cranking it, I turned on the key and watched the little red squiggle icon in the instrument panel until it shut off, indicating the engine's preheater had done its work; this took only a few seconds.

A 6-speed manual transmission is standard, but this truck had the optional Aisin 6-speed automatic, which shifts smoothly and keeps the engine at the best speed for whatever work it has to do. The transmission upshifts quickly enough to keep rpms low, so the engine usually runs between 1,700 and 2,100. A heavier foot tells the engine and tranny that you want to accelerate quicker and they oblige, delaying upshifts until 2,500 or 3,000 or whatever's needed to get you there when you want. I imagine that will be more the rule when the stout, steel IMI Dominator utility body on this test truck is crammed with heavy tools for whatever mission its eventual owner sends it on.

At first I found the truck a bit boring to drive because it was heavy and a bit ponderous, and the tranny upshifted whenever possible to lower revs and save fuel. However, switching on the Tow-Haul mode, done by fingering a pushbutton at the tip of the column-mounted shifter handle, livened things up. Upshift points stayed about the same, but the tranny downshifted more aggressively to help with braking - especially useful in city traffic.

Finger that pushbutton again and the two overdrive gears (5th and 6th) are cut off, which would be good on hilly city streets or while coming down a steep highway grade. Finger the button a third time and you're back to normal mode, with all six gears. It's easier to operate than it might sound, and less awkward than pulling the shift lever through multiple detents. As it is, the selector reads P-N-D-3-2-L, and thanks to that pushbutton, most of the time you can just leave it in Drive.

An exhaust brake is part of the sophisticated turbocharger's variable-vane function. You switch this on with a dash-mounted pushbutton. Take your foot off the accelerator and it begins retarding; downshifting to raise revs (which happens automatically in Tow-Haul mode) results in more retarding power. In this truck the turbo and brake were quiet, making no whistle or Jake Brake-like burble as in the 3500 HD. (Too bad.)

A power-take-off box is on the right side of the tranny case. Engineers say it's a good idea to order the PTO prep package (a $300 option) even if you don't need it, because someday you might, or the next owner will, and the package will add residual value to the truck. The PTO is engaged by a switch under the dashboard, while engine speed to run it is controlled by the cruise control switches in the steering wheel spokes. I didn't play with the PTO, though, and instead concentrated on driving.

Ride quality was good, with the suspension stiffness you'd expect in a midrange truck but with the body weight cancelling any harshness. Turning ability was surprisingly tight, even with the front-driving axle, and I made a U-turn using four lanes of a wide city street (from the left-turn lane to a few feet short of the curb, three lanes over). I didn't tape that circle, but it was probably under 50 feet.

A two-door single-seat Regular cab is standard, while this truck had the four-door Quad Cab, with a roomy front-seat area and real back seat that makes it capable of conveying up to six people. But the guys in back will need short legs to be comfortable, and a fire extinguisher bolted to the floor of this truck further interfered with leg room. The longer Maxi Cab would be a better idea for true crew-cab applications such as for line crews and firefighters, but the Mega is not offered in the 4500/5500 HD. However, these trucks will get a longer Ram Crew cab from the '09 Ram 1500 in the 2010 model year, Dodge sources say.

This cab had the mid-level SLT trim, with cool fabric seat covers and nice-looking two-tone gray plastic panels, just like in a Ram SLT pickup. Gauges are large and easy to read, with black-on-white numerals and red-orange accents on the needles. Many more numbers are available in a digital info display, though you have to learn to scroll through it. Among the icons that appears in a gauge is a red squiggle that lights up when the engine's being preheated for cold-temperature starts. HVAC controls are simple and effective rotary switches.

The driver's seat was part of a 40-20-40 split-bench setup. The "20" is a wide fold-down armrest with a compartment big enough to hold a laptop computer or vertical file folders (but not big enough to stow the remote-control box for the IMI crane, which sat on the passenger seat or the floor during my drives; the buyer will probably put it in one of the body's many cabinets). The driver's seat was comfortable, with bucket-like recesses to keep me in place, and with power controls, it can be raised and lowered to suit one's height.

I discovered the power-seat switches on the way to returning the big Ram to the Columbus dealer where I had picked it up. Is a power seat appropriate to a medium-duty truck? Sure. We all live better and why shouldn't the working guy who'll drive this rig? It's just one more thing for Dodge commercial-truck sales people to point out to prospective customers, who may well like what they see.